REGIONAL GRAVITY SURVEY OF ENUGU STATE

EXECUTIVE SUMMARY

A regional gravity survey of Enugu State was carried out in order to produce Bouguer anomaly, Free-air anomaly and the Elevation map of the State for mineral exploration. Acquisition of gravity data as a tool for mineral exploration is useful because gravity differences or anomaly reflect lateral density variation in rocks extending to several kilometres beneath the ground which interpretation reveals information about the subsurface geology. A total of 866 gravity stations were covered in an area of 7, 000km2 which gives a station density of 1 in 8km2 grids. Thirty-six evenly distributed gravity base stations were established across the entire State. These base stations were tied to the International Gravity Standardization Net (IGSN '71) through the Primary Gravity Network of Nigeria (PGNN). Result of this survey shows a good correlation between the Bouguer anomalies and the surface geology of Enugu State. The map indicate several gravity closures of various shapes and varied lateral extent defining both shallow and deep seated mineralized structures. A linear mineralized structure likely to be a fracture runs from Inyi through Agbani to Enugu and Eha-Amufu. This structure extends further east covering Awgu, Nara, Mpu and into Ebonyi State. Low gravity closures defining large deposit of gas can be observed around Opi and the surrounding towns. Other areas of interest to investors include Umulokpa, Aguobu, Ukpata and Afa characterized by an oval shaped gravity closure. Investors in Lead Zinc, Baryte, Limestone, Gas etc will find the Bouguer anomaly map very useful. They are advice to carry out detail investigation and modeling on some of the more important Bouguer anomalies in order to determine the geometry of the mineral ore before mining. The Free-air anomaly and the Elevation maps are recommended to surveyors and geodesists. Researchers and Investors in mineral resources carrying out gravity survey in Enugu State are recommended to tie their surveys to IGSN '71 through any of the established base stations in the State; this will greatly reduce errors in gravity surveys.